This invention relates to an improved process and apparatus for finishing, and more specifically abrading, a large number of parts, substantially in bulk treatment, for removing flash, burrs, sharp corners and surface contamination.
A wide variety of vibratory and tumbling processes and apparatus have been developed for finishing parts, and these known arrangements for the most part are reasonably efficient in their performance on some parts, particularly larger and more durable parts. The known arrangements, however, have proven less effective when dealing with large quantities of smaller parts and specifically those of more delicate materials such as plastics or powdered metals, and in particular those parts having complex configurations.
One of the most commonly used techniques for finishing parts involves a tumbling device such as an elongate barrel which rotates or moves generally about a horizontal axis, and the bulk quantity of parts is positioned in the barrel whereby they travel upwardly along one interior side of the barrel during rotation thereof, and then tumble back downwardly due to the effect of gravity. Tumblers of this type may be of a batch-type construction having a tumbling chamber in which a batch of parts is deposited, or may be of a flow-through construction having a generally spirally-shaped guide channel generated about the rotational axis so that the parts progressively move from an inlet end to an outlet end of the tumbler but the parts are otherwise treated in the same manner as in a batch-type tumbler. Many of these tumblers also use nozzles disposed interiorly thereof to effect blasting of the parts simultaneously with the tumbling thereof. These known arrangements, however, have been observed to be relatively violent in that the nature of the tumbling action makes it difficult to control the movement of the parts, and thus such arrangements have been observed to cause significant damage such as chipping and the like when the parts being processed are of a fragile or delicate nature. Such tumblers also are normally incapable of providing desired control over part movement since the nature of the overall movement of the bulk mass causes some parts to violently tumble downwardly along the top of the mass, whereas other parts slide backward at the bottom of the mass and hence are not properly exposed to the blasting spray.
Similar known tumbling devices involve angled moving belts which cause the bulk mass to move in a manner similar to a rotating barrel device and hence possess similar limitations.
With respect to known vibratory arrangements, the parts are typically positioned in a vibratory machine having an elongate and typically annular channel which contains not only the parts, but also a quantity of bulk abrasive media together with water or other liquid. Due to the vibration of the machine, the parts and bulk abrasive media function effectively as a flowable mass such that the parts and abrasive media are moved, typically in a progressive screw-like pattern along the length of the confining chamber as a result of the vibration of the apparatus. The gradual tumbling movement of the flowable mass causes the parts and abrasive media to continually rub and contact one another so as to effect surface finishing of the parts. While such vibratory arrangement is particularly desirable in that it is capable of handling and not severely damaging delicate parts, nevertheless such process is relatively slow in terms of performance time, is typically a wet process which requires additional secondary operations such as drying, and also requires substantial quantities of consumable abrasive media. This arrangement also is not as effective for finishing of complex shaped parts, specifically those having bores or holes therethrough due to the difficulty in effectively accessing such regions during tumbling of the flowable mass.
When utilizing tumblers for effecting blasting of parts as briefly described above, typical operation of the process normally results in overblasting of the batch of parts in order to effect blasting of all parts in the batch, which overblasting is required due to the nonuniformity of the blasting process and which results in some parts being excessively treated. This also results in the overall blasting process being of reduced efficiency due to the extended blasting time involved and the greater use requirements of abrasives.
With many prior processes and apparatus, particularly when surface finishing parts having complex contours and/or internal cavities, it has been necessary to physically individually fixture the parts in order to permit the parts to be acted on by appropriate tooling or blasting nozzles so as to permit surface treating of the complex part surfaces and specifically the interior cavity walls. The need to individually fixture and treat parts is obviously a very inefficient and time consuming process, but is a process which is frequently resorted to in view of the inability to effectively surface treat such parts using other known techniques.
Accordingly, it is an object of this invention to provide an improved process and apparatus for finishing, for example abrading, parts which particularly have a complex configuration or shape, and/or which may be of delicate or frangible material, with the improved process and apparatus of this invention overcoming many of the disadvantages associated with prior arrangements.
It is a further object of the invention to provide an improved process for finishing bulk parts by a continuous process which enables the parts to slowly move, as with a tumbling movement along a spiral path having closely adjacent convolutions, through a treating zone created by a blasting nozzle to permit a first-in first-out operation.
It is a still further object to provide a process, as aforesaid, which utilizes a vibratory device containing a narrow but elongate treating channel combined with a blasting nozzle which sprays, at high velocity, a preferably dry abrasive spray into the moving bulk mass in the channel to effect surface treating of the moving tumbling parts as they move through the spray zone.
More specifically, this invention relates to a process and apparatus wherein a bulk quantity of parts are positioned in a channel-like treating chamber which is subjected to vibration so as to cause the flowable mass of parts in the chamber to slowly undergo a corkscrew-like tumbling movement, whereby the parts are slowly and gently circumferentially tumbled around the transverse cross-section of the treating chamber while at the same time the flowable mass of parts is progressively moved lengthwise of the chamber. In a preferred embodiment, one or more nozzle arrangements are positioned directly over the treating chamber so that each nozzle has its discharge orifice position closely adjacent and directly above the flowing bulk mass in the chamber so as to effect a high-pressure blasting of a selected region of the flowing mass. The nozzle emits a downwardly-directed high-velocity spray which is defined by a carrier medium such as air having small abrasive particles or grit embedded therein. The abrasive spray contacts a reasonably small or concentrated area which has relatively small transverse and longitudinal extent over the flowing mass in the chamber. Due to its high-velocity discharge, the spray is effective in penetrating downwardly at least partway into the depth of the flowing mass. Accordingly, the slow corkscrew-like vibratory movement of the tumbling bulk mass causes and allows the orientation of the individual parts making up the mass to constantly change as they slowly move through the relatively small blasting zone defined below the nozzle, whereby the many different surfaces including edges and corners of the parts are thus subjected to the high-velocity abrasive spray which is effective for removing flash, burrs, sharp edges, surface oxides and the like.
In the improved process and apparatus of the present invention, as aforesaid, the blasting nozzle typically involves use of air as a media for effecting high-velocity discharge of solid abrasive media, and the velocity of the discharge from the blasting nozzle will normally be in the range of from about 80 to about 150 feet per second so as to achieve the desired abrading performance. In some instances, however, the carrier media for the abrasive as discharged from the blasting nozzle may comprise a liquid.
In the improved apparatus and process of this invention, as aforesaid, the vibrating apparatus includes an elongate treating channel which typically is circular or arcuate and is subject to vibration in a conventional manner so as to effect gradual and gentle corkscrew-like tumbling of the flowable mass in the lengthwise extent of the channel, and in many instances a plurality of blasting nozzles are positioned in longitudinally spaced relationship along and typically above the channel to permit subsequent treating of the flowable mass as it slowly tumbles and longitudinally advances along the channel. The sequentially positioned blasting nozzles can themselves be utilized to supply different types of blasting media so as to permit the flowable mass to be progressively abraded using different blasting media, such as finer or softer media as the flowable mass approaches its discharge time or location.
With the improved process and apparatus of the present invention, by causing the abrasive media to be blasted into the slowly tumbling bulk mass of parts which slowly move into and through a small and concentrated blasting zone, the use of carrier media such as air or water as well as the higher pressure thereof necessary to effect high discharge velocity, and the quantity of solid abrasive media which is intermixed in the discharged spray, can be optimized in terms of both efficient use and overall performance, and at the same time the tumbling of the mass of bulk parts is sufficiently gentle as to minimize damage to the parts as a result of both the tumbling and blasting thereof.
In the improved process and apparatus of the present invention, the blasting nozzle may be positioned at various locations relative to the elongate treating channel so as to optimize the overall treating effect. For example, while positioning the blasting nozzle above the channel will normally be a preferred location, nevertheless in some situations the nozzle may be disposed so as to discharge directly into the flowable mass within the channel, such as by disposing the nozzle so that it is oriented to discharge directly through the wall of the channel, such as through a side or bottom wall of the channel. In addition, the blasting nozzle may utilize any conventional technique for introducing the abrasive into the discharged fluid stream, such as either a conventional vacuum or aspiration-type nozzle which effectively sucks the abrasive into the fluid stream, or a conventional pressure-type nozzle which effectively causes the abrasive under pressure to be injected into the discharged fluid stream. In addition, in some applications the overall finishing performance may be vastly improved by intermixing the bulk parts with a plurality of inert flowable tumbling elements such as polyurethane elements which are relatively inert when subjected to the abrasive media discharged by the blasting nozzle, whereby the flowable mass defined by the inert tumbling elements and the parts being treated thus provides increased or optimized spacing and tumbling of the parts and hence increased treating thereof by the abrasive media as the parts flow through the blasting zones.
Other objects and purposes of the present invention will be apparent to persons familiar with processes and arrangements of this general type upon reading the following specification and inspecting the accompanying drawings.